gpio connection..need help

hi,i'm currently doing water level detector using de2 board.I want to connect buzzer as output to gpio..i want to assign it to my water level detector output which the buzzer will turn on when the water level is at highest level. i already have the output displayed on lcd and seven segment but now i'm not sure how can i assign it to turn on the buzzer. do i need to do coding to enable/disable the gpio? when i simply connect the buzzer, it always produce the sound..can anyone help me how to make the buzzer only turn on at the highest water level?

thanks....